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b=jn+8BxzapCfSwVMpqOVrLOZ4g/NyDmvoTdeW4qGt57C25b14nnqtxoeXURRwx3aLi syf1X+hLjQeFHHz8CBIS3julLE64HitmPcnC7fcC8W96wgM8Og4XkvNNHpk/0rU5LC XYeyPOqBxn1cqTYKph9J38q7eccnOjgorbo3lvl4= Date: Fri, 29 Aug 2025 20:09:53 -0700 From: Andrew Morton To: Wei Yang Cc: david@redhat.com, lorenzo.stoakes@oracle.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH] selftests/mm: directly add pagesize instead of increase until page size Message-Id: <20250829200953.1757e85542b1126c4881d600@linux-foundation.org> In-Reply-To: <20250830023102.14981-1-richard.weiyang@gmail.com> References: <20250830023102.14981-1-richard.weiyang@gmail.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 1BD081C0003 X-Rspamd-Server: rspam04 X-Rspam-User: X-Stat-Signature: kwdj6seu5k1xkkq368qies39oczgrwah X-HE-Tag: 1756523395-327618 X-HE-Meta: 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 IjLmtNnR n0q+T/c5sLtIbekJqjXf7WO/hkl9HsrRaUk0CZaRozmYlKbcPi8XvE8H65q38cDDelZX4BQ5Xcr8IgPyd+X0N69y7YsuB7uyaLWkZFiDi40MGpCcuIs/ns0foTVzITPp+LDHs8GHc7ygoiLaz1YgY/fuYq1TsC1RBhG+a5M1wV97mp7CeGGf0YhmD6NDtETVPnG4pm3ojom9uRABlnnn2//ROkzPP3EZluH1TclSSWwdkeKXfF3/uvSpyfq6C/tSh4bNQ1LEpddhAHuI2Ato8Oq+iAX7WYJRHSFj73/oCO5cj+umFbWFac+VIWRJja5+H3MbuM1bsHnB4tmo/DDxyC9tXeg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, 30 Aug 2025 02:31:02 +0000 Wei Yang wrote: > The check of is_backed_by_folio() is done on each page. > > Directly move pointer to next page instead of increase one and check if > it is page size aligned. Why? > --- a/tools/testing/selftests/mm/split_huge_page_test.c > +++ b/tools/testing/selftests/mm/split_huge_page_test.c > @@ -423,9 +423,8 @@ static void split_pte_mapped_thp(void) > > /* smap does not show THPs after mremap, use kpageflags instead */ > thp_size = 0; > - for (i = 0; i < pagesize * 4; i++) > - if (i % pagesize == 0 && > - is_backed_by_folio(&pte_mapped[i], pmd_order, pagemap_fd, kpageflags_fd)) > + for (i = 0; i < pagesize * 4; i += pagesize) > + if (is_backed_by_folio(&pte_mapped[i], pmd_order, pagemap_fd, kpageflags_fd)) > thp_size++; Looks like we're doing more work. Is there something wrong with the existing code?